Aircraft seats have specific performance requirements that generally relate to weight and crash loads, typically requiring low weight and high strength. These performance requirements are often significant drivers of seat design, especially in seats including integral occupant restraints.
The performance requirements are not always aligned with seat comfort. For instance, to attempt to accommodate occupant comfort, current aircraft seats are able to recline by changing the angle of the seat back. In such a traditional aircraft seat, as the seat back is reclined, increasing frictional force is required under the occupant's backside to keep the occupant from sliding out of the seat. This friction uncomfortably tugs on clothing, can lead to the occupant sliding forward, and may create a gap in the lumbar region of the back or spine. This leads to back fatigue, discomfort, loss of concentration, and the possibility of injury.
Another typical concern with aircraft seats, and specifically flight deck seats, is the ability of the pilot to fully extend his or her legs to fully actuate the rudder pedals of the aircraft. In current aircraft seats, this need is addressed through complicated mechanisms that “give-way” under load. These systems, unfortunately, are often poorly designed from an ergonomic perspective and are not well-understood by users, causing misuse and reduced comfort.
Traditional back cushions used for flight deck seats include thick, in some instances contoured foam cores with lateral/side bolstering. These cushion designs are frequently adapted from automobiles or ground vehicles. During cornering, ground vehicle occupants experience lateral acceleration or force. However, aircraft do not generate any significant lateral load or force, as turns are primarily executed by rolling the aircraft about its longitudinal axis. This rolling motion keeps the acceleration or force associated with turning in a vertical orientation relative to the aircraft seat. Thus, lateral or side bolsters as used in ground vehicles and traditional aircraft seats are largely unnecessary in an aircraft, and represent a size-limiting feature that may create comfort issues for larger occupants. The non-integrated design of current aircraft seats requires the use of thick foam cushion cores that are contoured, with or without side bolstering, to provide a suitable occupant interface. Thus, the extra thickness of foam is detrimental to the overall weight of the seat, which is a significant performance metric.
Current flight deck seats for aircraft also employ poor ergonomic adjustment mechanisms for tailoring the support of the back cushion. Some currently available seats include adjusters that allow the occupant to move the entire back cushion up and down, as well as to recline the entire cushion relative to the remainder of the seat back structure such that the bottom edge of the back cushion is thrust forward toward the occupant's lower back. Unfortunately, occupants do not typically have a back shape consistent with the first form of adjuster. Other currently available seats include an adjustable lumbar support widely used in automotive applications to provide lumbar “support” by pushing the back cushion out in an attempt to force proper back curvature. With respect to these seats, however, it has been found that pressure applied in the lumbar area of the back does not necessarily result in healthy posture, and the lumbar curvature pressure application location varies more over a range of occupant sizes as compared to the lumbosacral area, which varies less over the same range.
There is a need for an aircraft seat that improves occupant comfort but continues to meet the performance requirements of an aircraft seat.